The present invention relates to an asynchronous transfer mode (ATM) traffic control framework based on an integrated usage parameter control (UPC) approach. Specifically, the UPC approach provides a unified and scalable solution to the issue of quality-of-service (QOS) levels both over a range of anticipated services and during periods of network overload.
Future broadband networks will be required to support new bandwidth intensive applications such as full motion video, teleconferencing, interactive multimedia, medical imaging, scientific visualization, distributed computing, distributed simulation, client server traffic, etc. These applications will place varying requirements in terms of the quality-of-service they receive from the network. Asynchronous transfer mode (ATM) technology is now viewed as the primary switching and transport technology for emerging high-speed networks, both in wide-area and local-area scenarios. While ATM offers the ability to support a range of multi-rate services in an integrated manner, technical approaches for maintaining quality-of-service in dynamic and heterogeneous traffic environments require further development and standardization.
In spite of the the promise of abundant bandwidth, ATM may not be able to satisfactorily support many QOS sensitive services unless appropriate dynamic traffic control is exercised by the network. The underlying philosophy of ATM networking is fast generic cell transport with simple switching nodes that scale easily with line speed and number of ports. The cell-level control in these nodes is generally quite minimal to avoid complex high-speed processing. Application specific switching node architectures are considered to be neither desirable nor necessary. The lack of strong cell level controls at each ATM switching node, coupled with the fact that ATM based switches have a limited amount of buffering (due to technological as well as scaling limitations), can result in traffic hot spots and other congestion related problems within the network. Further, the cell-based nature of the transport can result in server performance degradation under over-load due to cell loss and consequent retransmission of data.
The applications anticipated in broadband networks have traffic characteristics that are very different from those of current applications. Many of these applications require rapid movement of large quantities of data across the network, which can overwhelm the buffers in the ATM switches, resulting in cell loss. Further, the cell-based nature of the transport can result in severe performance degradation under overload due to cell loss and consequent retransmission of data. While providing more memory in the network may temporarily alleviate the problem, it does not lead to a scalable solution. For example, FIG. 1 shows the performance of an ATM multiplexer (without link level controls), that multiplexes traffic from 16 FDDI routers. Each router has an access rate of 100 Mbits/second to the ATM multiplexer, and the FDDI packets have an average size of 4 Kbytes. Even at utilizations as low as 60%, and with a buffer size of 200 cells, the frame loss rate is of the order of 1.0.times.10.sup.-1, which would be unacceptable for most data applications. With a larger buffer size of 1000 cells the frame loss rate is of the order of 1.0.times.10.sup.-3. Thus additional buffers do not mitigate the problem. Controlled movement of data across the network is essential to ensure high throughput and low loss.